holes in a direction perpendicular to the former, as the number of sheaves it is to have; these holes being intended as the commencement of the several mortises to contain the sheaves.

The blocks are next mortised in three mortising engines, which elongate the holes abovementioned to their proper dimensions. Here the motion of the sliding frame for the chisels is communicated to it by means of a long working beam or lever, extending the whole length of the frame at the top of it. At one end it is united by a connecting rod with the chisel frame; and at the other it is fixed to an axis, which is supported by the framing, and which forms its centre of motion. A connecting rod is joined to it in the middle of the beam; the lower end of which is worked by a crank, formed in the middle of the main axis, which is situated in a direction perpendicular to that which we have described, and is supported in the framing. It is provided with a cone for casting off the movement. The engine with the beam acts with surprising rapidity, making upwards of 400 strokes per minute, at every one of which it cuts out a chip from each mortise as thick as pasteboard. Its movement is, indeed, so rapid, that the chisels cannot be distinctly seen when it is at work; so that the mortises seem to lengthen, and chips to fall out, without any evident cause.

The angles of the blocks are next cut off by three circular saws, as preparatory to reducing them to the elliptical figure. The outside surfaces of the block are then formed to their true figure by three shaping engines, each of which forms every part of ten blocks simultaneously.

The scores, or grooves, round the block are next formed, to receive the rope or strap by which they are suspended; this is effected by two scoring engines.

Then the blocks are trimmed by manual labour, to smooth and polish them.

In order to make the sheaves, the first process is cutting pieces or flakes off the end of the trees of lignum vitæ, of a suitable thickness to form the sheaves. This is accomplished by a reciprocating and two circular saws. These flakes are made circular, and the centres pierced in two rounding and centering machines, or trepan saw.

A hole is next excavated in the centre of each sheave, to inlay the coak or piece of bell metal, which is fitted into the centre of each sheave, to form a socket for the centre pin. The centre holes through the coaks are next broached out to a true cylinder in three broaching machines.

The last process is turning the faces and edges of the sheaves to a flat surface, in three facing lathes, which also form the

groove round the edges for them, for the rope which encompasses them when in the block.

There are also two machines for making what are denominated dead eyes, which are very ingenious and complete. The whole number of machines here employed is 47. To describe them minutely would require a volume. A good account of them, illustrated by excellent engravings, may be seen in Rees's New Cyclopædia, art. MACHINERY.

BORING of Cylinders, Ordnance, Wooden Pipes, &c. See CYLINDERS, ORDNANCE, and PIPES.

BRAMAH'S MACHINE, Bramah's Hydrostatic Press, &c. -names which are now commonly given to the contrivances of Mr. Bramah of Piccadilly, by which he applied the quaqua versum pressure of fluids as a very powerful agent in many kinds of machinery requiring motion and force. These contrivances (for which Mr. Bramah took out a patent in March 1796) consist in the application of water, or other dense fluids, to various engines, so as, in some instances, to cause them to act with immense force; in others, to communicate the motion and powers of one part of a machine to some other part of the same machine; and, lastly, to communicate the motion and force of one machine to another, where their local situations preclude the application of all other methods of connection.

The first and most material part of this invention will be clearly understood by an inspection of fig. 4. pl. IX. where "A is a cylinder of iron, or other materials, sufficiently strong, and bored perfectly smooth and cylindrical; into which is fitted the piston B, which must be made perfectly water-tight, by leather or other materials, as used in pump-making. The bottom of the cylinder must also be made sufficiently strong with the other part of the surface, to be capable of resisting the greatest force or strain that may at any time be required. In the bottom of the cylinder is inserted the end of the tube c; the aperture of which communicates with the inside of the cylinder, under the piston B, where it is shut with the small valve D, the same as the suction-pipe of a common pump. The other end of the tube c communicates with the small forcing-pump or injector E, by means of which water or other dense fluids can be forced or injected into the cylinder A, under the piston B. Now, suppose the diameter of the cylinder A to be 12 inches, and the diameter of the piston of the small pump or injector E only one quarter of an inch, the proportion between the two surfaces or ends of the said pistons will be as 1 to 2304; and supposing the intermediate space between them to be filled with water or other dense fluid capable of sufficient resistance, the force of one piston will act on the other just in the above proportion,

viz. as 1 is to 2304. Suppose the small piston in the injector to be forced down when in the act of pumping or injecting water into the cylinder A, with the power of 20 cwt. which could easily be done by the lever н; the piston в would then be moved up with a force equal to 20 cwt. multiplied by 2304. Thus is constructed a hydro-mechanical engine, whereby a weight amounting to 2304 tons can be raised by a simple lever, through equal space, in much less time than could be done by any apparatus constructed on the known principles of mechanics; and it may be proper to observe, that the effect of all other mechanical combinations is counteracted by an accumulated complication of parts, which renders them incapable of being usefully extended beyond a certain degree; but in niachines acted upon or constructed on this principle every difficulty of this kind is obviated, and their power subject to no finite restraint. To prove this, it will be only necessary to remark, that the force of any machine acting upon this principle can be increased ad infinitum, either by extending the proportion between the diameter of the injector and the cylinder A, or by applying greater power to the lever H.

66

Fig. 5. represents the section of an engine, by which very wonderful effects may be produced instantaneously by means of compressed air. AA is a cylinder, with the piston B fitting air-tight, in the same manner as described in fig. 4. c is a globular vessel made of copper, iron, or other strong materials, capable of resisting immense force, similar to those of air-guns. D is a strong tube of small bore, in which is the stop-cock E. One of the ends of this tube 'communicates with the cylinder under the piston B, and the other with the globe c. Now, suppose the cylinder A to be the same diameter as that in fig. 4. and the tube D equal to one quarter of an inch diameter, which is the same as the injector fig. 4.: then, suppose that air is injected into the globe c (by the common method), till it presses against the cock E with a force equal to 20 cwt. which can easily be done; the consequence will be, that when the cock E is opened the piston в will be moved in the cylinder AA with a power or force equal to 2304 tons; and it is obvious, as in the case fig. 4. that any other unlimited degree of force may be acquired by machines or engines thus constructed.

"Fig. 6. is a section, merely to shew how the power and motion of one machine may, by means of fluids, be transferred or communicated to another, let their distance and local situation be what they may. A and B are two small tubes, smooth and cylindrical; in the inside of each of which is a piston, made water and air-tight, as in figs. 4. and 5. cc is a tube conveyed under ground, or otherwise, from the bottom of one cylinder to

the other, to form a communication between them, notwithstanding their distance be ever so great; this tube being filled with water or other fluid, until it touch the bottom of the piston; then, by depressing the piston A, the piston в will be raised. The same effect will be produced vice versa: thus bells may be rung, wheels turned, or other machinery put invisibly in motion, by a power being applied to either.

"Fig. 7. is a section, shewing another instance of communicating the action and force of one machine to another; and how water may be raised out of wells of any depth, and at any distance from the place where the operating power is applied. A is a cylinder of any required dimensions, in which is the working piston B, as in the foregoing examples: into the bottom of this cylinder is inserted the tube c, which may be of less bore than the cylinder A. This tube is continued, in any required direction, down to the pump cylinder D, supposed to be fixed in the deep well EE, and forms a junction therewith above the piston F; which piston has a rod G, working through the stuffing-box, as is usual in a common pump. To this rod Gis connected, over a pulley or otherwise, a weight H, sufficient to overbalance the weight of the water in the tube c, and to raise the piston F when the piston B is lifted: thus, suppose the piston B is drawn up by its rod, there will be a vacuum made in the pump cylinder D, below the piston F; this vacuum will be filled with water through the suction pipe, by the pressure of the atmosphere, as in all pumps fixed in air. The return of the piston B, by being pressed downwards in the cylinder a, will make a stroke of the piston in the pump cylinder D, which may be repeated in the usual way by the motion of the piston B, and the action of the water in the tube c. The rod G of the piston F, and the weight H, are not necessary in wells of a depth where the atmosphere will overbalance the water in the suction of the pump cylinder D, and that in the tube c. The small tube and cock in the cistern I are for the purpose of charging the tube c." By these means it is obvious most commodious machines of prodigious power, for tearing up trees, &c. and susceptible of the greatest strength, may readily be formed. If the same multiplication of power be attempted by toothed wheels, pimons, and racks, it is scarcely possible to give strength enough to the teeth of the racks, and the machine becomes very cumbersome and of great expence. But Mr. Bramah's machine may be made abundantly strong in very small compass. It only requires very accurate execution. Mr. Bramah, however, was greatly mistaken when he published it as the discovery of a new mechanic power. The principle on which it depends has been well known for nearly two centuries; and it is

matter of surprise that it has never before been applied to any useful practical purpose.

CAMEL is the name given to a machine employed by the Dutch for carrying vessels heavily laden over the sand-banks in the Zuyder-Zee. In that sea, opposite to the mouth of the river Y, about six miles from the city of Amsterdam, there are two sand-banks, between which is a passage called the Pampus, sufficiently deep for small vessels, but not for those which are large and heavily laden. On this account ships which are outward bound take in before the city only a small part of their cargo, receiving the rest when they have got through the Pampus. And those that are homeward bound must, in a great measure, unload before they enter it. For this reason the goods are put into lighters, and in these transported to the warehouses of the merchants in the city; and the large vessels are then made fast to boats, by means of ropes, and in that manner towed through the passage to their stations.

Though measures were adopted so early as the middle of the sixteenth century, by forbidding ballast to be thrown into the Pampus, to prevent the further accumulation of sand in this passage, that inconvenience increased so much from other causes as to occasion still greater obstruction to trade; and it at length became impossible for ships of war, and others heavily laden, to get through it. About the year 1672 no other remedy was known than that of making fast to the bottoms of ships large chests filled with water, which was afterwards pumped out; so that the ships were buoyed up, and rendered sufficiently light to pass the shallow. By this method, which was attended with the utmost difficulty, the Dutch carried out their numerous fleet to sea in the abovementioned year. This plan, however, gave rise soon after to the invention of the camel, by which the labour was rendered easier.

The camel consists of two half ships, constructed in such a manner that they can be applied below water, on each side of the hull of a large vessel. On the deck of each part of the camel are a great many horizontal windlasses, from which ropes proceed through apertures in the one half, and, being carried under the keel of the vessel, enter similar apertures in the other, from which they are conveyed to the windlasses on its deck. When they are to be used, as much water as may be necessary is suffered to run into them; all the ropes are cast loose, the vessel is conducted between them, and large beams are placed horizontally through the port-holes of the vessel, with their ends resting on the camel on each side. When the ropes are made fast, so that the ship is secured between the two t, so that thi